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Biomedical subjects

J Henriksson

Publications and source records attributed to J Henriksson.

At least 55 records · Page 3Linked to original sources
PubMed1995

Trypanosoma cruzi exoantigen is a member of a 160 kDa gene family.

During the chronic stage of Chagas disease a 160 kDa antigen appears in the blood of patients and remains detectable many years after the onset of the disease. This antigen is secreted by the trypomastigote form of the parasite while it is undetectable in the epimastigote form. We report here that the chronic 160 kDa exoantigen is encoded by a gene family (CEA 160 family). We describe the cloning and partial nucleotide sequence of a gene (CEA 160-1) belonging to the CEA160 family. Comparison of the gene sequence with other sequences present in the databases revealed homologies with several Trypanosoma cruzi surface antigens. Highest amino acid identity (59%) was with members of a family containing epitopes that mimic nervous tissues (Van Voorhis et al. 1993). Another related group (18-22% amino acid identity) comprises proteins of 85 or 160 kDa sharing an amino acid motif that is conserved among bacterial neuraminidases (Fouts et al. 1991; Pollevick et al. 1991; Kahn et al. 1991; Takle & Cross, 1991; Franco et al. 1993). The amino acid identities with the different antigens were not homogeneously distributed. Regions of higher identity (40-60%) were grouped in the central region of each protein.

Amino Acid Sequence↗
PubMed1995

Effect of training and nutrition on the development of skeletal muscle.

Recent data suggest that an increased muscle mitochondrial oxidative capacity is not a prerequisite for a marked metabolic effect of endurance training, but instead may represent an adaptive phenomenon to the new metabolic situation. The muscle content of the glucose transporter GLUT-4 increases after one or only a few exercise sessions. The ensuring enhancement of the insulin sensitivity allows faster replenishment of muscle glycogen stores following exercise bouts. There is evidence that the muscle content of GLUT-4 declines more slowly with inactivity than the muscle oxidative capacity. This may be a sign that, as in the chronically stimulated rabbit muscle, adaptive changes in human skeletal muscle follow a "first-in, last-out' sequence. There is evidence that muscle (and possibly also plasma) triacylglycerol is more important as an energy source during exercise than was previously recognized. Endurance training increases the content of slow isoforms of myosin in the muscle, and information on changes in muscle shortening velocity and on the molecular regulation of muscle volume is emerging. beta 2-agonists are well documented to enhance muscle mass, whereas creatine supplementation appears to enhance performance during high-intensity exercise.

Adaptation, Physiological↗
PubMed1995

Muscle blood flow in cats: comparison of microdialysis ethanol technique with direct measurement.

A quantitative validation of the microdialysis ethanol technique was performed in cat gastrocnemius muscle. Six to eight microdialysis probes were inserted into the isolated muscle preparation and perfused (0.5-10.0 microliters/min) with Krebs-Henseleit buffer containing between 5 and 1,000 mmol/l ethanol. Skeletal muscle blood flow was held constant in the range of 4-99 ml.100 g-1.min-1 by a servo-controlled roller pump and was determined with the microdialysis ethanol technique as well as by timed collection of venous outflow. The ethanol concentration outflow-to-inflow ratio ([ethanol]collected dialysate/[ethanol]infused perfusion medium) decreased in a nonlinear fashion when microdialysis perfusion flow rates of 0.5 and 1.0 microliter/min were employed. However, a linear decrease was found between 4 and approximately 45 ml.100 g-1.min-1 (r = -0.92 to -0.99). The lower outflow-to-inflow ratio was at 4 ml.100 g-1.min-1 (i.e., due to a low probe perfusion flow rate or a large dialysis membrane), the greater the sensitivity of the method was. It is concluded that this nonradioactive technique provides a simple and valid method for determining nutritive blood flow in skeletal muscle.

Animals↗
PubMed1995

A mathematical model for measuring blood flow in skeletal muscle with the microdialysis ethanol technique.

A theoretical analysis of the microdialysis ethanol technique in skeletal muscle is presented, and a model governing the transport of ethanol from the microdialysis probe to the capillaries in the muscle tissue is proposed. The model is derived under the assumption of a steady-state situation, and an analytical solution is found for the outflow-to-inflow ratio of ethanol in the perfusate. Theoretically calculated results are compared with experiments, and for at least one of the two probe types used good agreement is achieved in a wide range of blood flow and perfusate flow rates. The main uncertainty factor in the theoretical calculations is the diffusivity of ethanol in muscle tissue, and the value for best agreement between theory and experiments has been used. Error estimates show that for a constant relative error in the outflow-to-inflow ratio of ethanol in the perfusate, low perfusate flow rates give better predictions of the blood flow.

Animals↗
PubMed1995

Metabolic enzyme activity in the quadriceps femoris muscle in patients with severe chronic obstructive pulmonary disease.

Eighteen patients with severe COPD and seven healthy control subjects 64.0 +/- 2.2 and 66.8 +/- 1.4 yr of age, respectively (mean +/- SEM), were investigated. Arterial blood gas analysis, dynamic lung volumes, and muscle biopsy specimens from the quadriceps femoris muscle were performed. The muscle biopsies were analyzed for citrate synthase (CS), succinic acid dehydrogenase (SDH), 3-hydroxyacyl-CoA dehydrogenase (HAD), phosphofructokinase (PFK), and lactate dehydrogenase (LDH) activities and related to protein content. The PFK activity was higher in the COPD group than in the control group (+34%, p < 0.05). CS showed a group difference in the opposite direction (-29%, p < 0.05). LDH activity followed PFK and tended to be higher in the patient group (+27%, NS), whereas SDH (-31%, NS) and HAD (-28%, NS) mirrored the CS results. Muscle protein concentration tended to be lower in the COPD group (-14%, NS). There were no significant changes in enzyme activity after 7 mo of long-term oxygen therapy (n = 6). These results indicate adaptation in the form of augmented glycolysis (PFK), and decreased aerobic metabolism (CS) in the quadriceps femoris muscle in patients with advanced COPD.

Citrate (si)-Synthase↗
PubMed1995

Influence of exercise on insulin sensitivity.

An important determinant of insulin sensitivity in humans, the insulin-induced glucose uptake in skeletal muscle (directed into glycogen synthesis), has been found to be markedly enhanced in endurance-trained individuals compared with sedentary controls. This enhanced insulin action is accompanied by a decreased insulin response during an oral glucose load. Available evidence indicates that the enhanced insulin action is not a genuine training effect, but merely a lasting effect of the previous exercise session(s). In the young, insulin sensitivity increases with a single exercise session, but the increase may appear only after several training sessions in middle-aged or older individuals. The effect disappears after 3-6 days. The exercise-induced reduction in muscle glycogen is an important factor underlying the increased insulin sensitivity in the period after exercise. There are reports that endurance and strength training enhances whole-body insulin sensitivity to a similar extent, and available evidence suggests that, provided total energy expenditure is held constant, low-intensity and high-intensity exercise are equally effective in promoting insulin sensitivity. Differences in sex steroids may explain the observation of a markedly higher insulin sensitivity in women than in men. Adaptations, which might underlie the increased insulin sensitivity in trained individuals, include increases in levels of the glucose transporter protein GLUT-4 and in muscle glycogen synthase activity, a decrease in the serum triglyceride concentration and, possibly, an increase in the muscle capillary network.

Adaptation, Physiological↗
PubMed1994

A gene family encoding heterogeneous histone H1 proteins in Trypanosoma cruzi.

A gene family encoding a set of histone H1 proteins in Trypanosoma cruzi is described. The sequence of 3 genomic and 4 cDNA clones revealed the presence of several motifs characteristic of histone H1, although heterogeneity at the polypeptide level was evident. The clones encode histone H1 proteins of an unusually small size (74-97 amino acids), which lack the globular domain found in histone H1 of higher eukaryotes. All histone H1 mRNAs from T. cruzi are polyadenylated, although no typical polyadenylation signal was found. Furthermore, the genes encoding the histone H1 proteins in T. cruzi are found in a tandem array containing 15-20 gene copies per haploid genome. This tandem array is located on a large chromosome of 2.2 Mb.

Amino Acid Sequence↗
PubMed1994

Muscle blood flow during intermittent exercise: comparison of the microdialysis ethanol technique and 133Xe clearance.

1. Local skeletal muscle blood flow was monitored using the microdialysis ethanol technique and 133Xe clearance during intermittent isometric contractions (5 s on/10 s off) of the thigh at 0-60% of the maximal voluntary isometric contraction force. 2. A linear increase in blood flow over a 25-fold range was detected using both 133Xe clearance and the microdialysis ethanol technique. 3. The median correlation coefficient between percentage maximal voluntary isometric contraction force and the ethanol outflow/inflow ratio, a marker of blood flow, was r = -0.98 (-0.94 to -0.99) (median and range, n = 6). The corresponding correlation coefficient for 133Xe clearance was r = 0.97 (0.92-0.98), the correlation coefficient between the ethanol outflow/inflow ratio and 133Xe clearance being r = -0.92 (-0.89 to -0.94). 4. Dialysate glucose concentration, although affected by blood flow, was not always significantly correlated with blood flow changes (r = 0.70; 0.51-0.95). 5. It may be concluded that the ethanol technique provides a valid measure of changes in local skeletal muscle blood flow. The data furthermore show that a linear increase in thigh skeletal muscle blood flow exists during the studied protocol of intermittent isometric contractions.

Adult↗
PubMed1994

Regulation of skeletal muscle blood flow during acute insulin-induced hypoglycemia in the rat.

The mechanism behind hyperemia in skeletal muscle during insulin-induced hypoglycemia was investigated in 42 anesthetized male Wistar rats using the microdialysis ethanol technique of monitoring nutritive blood flow. Microdialysis probes were inserted bilaterally into the gastrocnemius muscle and perfused with a modified Krebs-Henseleit buffer containing 20 mmol/l ethanol and one or more of the following compounds: propranolol (10(-6) mol/l), phentolamine (10(-6) mol/l), and calyculin A (1.0 mumol/l). Muscle blood flow increased, as indicated by a decrease in the ethanol outflow:inflow ratio (P < 0.001, n = 6), during hypoglycemia induced by a bolus intravenous infusion of insulin (680 mU/kg body wt). This increase was not present during normoglycemia or during hypoglycemia and local beta-adrenergic blockade via propranolol. However, the hyperemic response was potentiated during hypoglycemia and local alpha-adrenergic blockade via phentolamine. A normal hyperemic response to hypoglycemia was detected during simultaneous alpha- and beta-adrenergic blockade. This response was eliminated on further supplementation of the microdialysis perfusion medium with calyculin A. Therefore, although stimulation of the alpha- and beta-adrenergic receptors does occur during insulin-induced hypoglycemia, it is not essential for the induction of hyperemia in this state. It may be concluded that hyperinsulinemia results in vasodilatation during hypoglycemia, although hyperinsulinemia does not have an effect on skeletal muscle blood flow under normoglycemic conditions.

Acute Disease↗
PubMed1993

Trypanosoma cruzi: correlation between karyotype variability and isoenzyme classification.

Forty-three Trypanosoma cruzi isolates from Chile and Colombia and three cloned stocks from Bolivia and Brazil were studied at the karyotype level by hybridization with four different parasite gene probes to chromosomes separated by pulsed-field gel electrophoresis. The results showed that classification of parasite isolates based on isoenzyme analysis at 12 or more genetic loci correlated with the classification obtained by molecular karyotype analysis. However, less correlation was found between molecular karyotypes and the zymodemes Z1, Z2Bra, Z2Bol, and Z3 based on analysis at only two genetic loci. All the four probes used in this study allowed differentiation between different T. cruzi stocks but the SAPA and the antigen 13 probes were most informative. Isolates which were unclassified at the isoenzyme level were also studied and in most cases similar hybridization patterns were observed as obtained with one or more isoenzyme-classified isolates. The results demonstrate the potential of using molecular karyotyping as a tool for classification. A few pulsed-field gel electrophoresis hybridization experiments provide the same information as obtained by isoenzyme analysis using a dozen or more enzymes. The clonal theory of T. cruzi propagation is supported by our results since the strong correlation between isoenzyme classification and molecular karyotype is difficult to explain with a sexual mode of replication. No minichromosomes were detected in any of the T. cruzi samples studied. Neither was any strong correlation found between the clinical manifestations of Chagas' disease and the molecular karyotypes of the T. cruzi isolates.

Animals↗
PubMed1993

Isolation and characterization of a gene from Trypanosoma cruzi encoding a 46-kilodalton protein with homology to human and rat tyrosine aminotransferase.

The complete sequence of a gene encoding a 46-kDa protein of Trypanosoma cruzi is presented. The first ATG complies with the consensus sequence for initiation of translation. A single band of 2 kb was highlighted by hybridizing a probe from the 46-kDa protein gene to a Northern filter containing total T. cruzi RNA. The gene is present in 50-80 copies per cell and most of them are contained in 2 tandem arrays on large T. cruzi chromosomes (> 2000 kb). A strong homology with rat and human tyrosine aminotransferase was detected. Homology with a Trypanosoma brucei retrotransposon was found in the nonsense strand of the intergenic region.

Amino Acid Sequence↗
PubMed1993

Interstitial glucose and lactate balance in human skeletal muscle and adipose tissue studied by microdialysis.

1. Microdialysis was used to gain insight into the substrate exchanges in the interstitial space of skeletal muscle and adipose tissue. Probes were inserted in the quadriceps femoris muscle and para-umbilical subcutaneous adipose tissue of thirteen subjects and microdialysis was performed at different flow rates (1-4 microliters min-1) and during changes in tissue blood flow. 2. When ethanol (5 mM) is included in the perfusion solution, the ethanol clearance from the probe is a measure of tissue blood flow. Blood flow changes induced by adenosine or vasopressin perfusion, by exercise or by circulatory occlusion resulted in ethanol clearance values of 69-139% of the basal level. The ethanol clearance was higher in skeletal muscle than in adipose tissue (32-62%, P < 0.001), a difference compatible with a higher blood flow in muscle tissue. 3. The fraction of the interstitial glucose concentration that was recovered with the microdialysis was similar in skeletal muscle (the absolute values being 1.70 +/- 0.14 mM at 1 microliter min-1 and 0.59 +/- 0.05 mM at 4 microliters min-1) and adipose tissue (1.89 +/- 0.20 mM at 1 microliter min-1; 0.54 +/- 0.05 mM at 4 microliters min-1) and correlated inversely with the tissue ethanol clearance, both in the basal state and during changes in tissue blood flow (muscle: r = -0.56 to -0.67; adipose tissue r = -0.72 to -0.95). Coefficients of variation were 6-8% (glucose) and 11-16% (lactate) and were similar during isometric exercise. The reproducibility of the technique (comparison of two contralateral probes; perfusion flow rate 4 microliters min-1) was 5.3-8.3% (ethanol) and 23.9-20.8% (glucose) in muscle (n = 6) and adipose tissue (n = 4) respectively. 4. The skeletal muscle dialysate lactate concentration (1 microliter min-1: 1.16 +/- 0.2 mM) was higher than in adipose tissue (0.76 +/- 0.08 mM, P < 0.05), where the absolute amount of lactate that could be removed from the tissue (at 4 microliters min-1) was only half of that in skeletal muscle (0.8 +/- 0.11 vs. 1.76 +/- 0.23 nmol min-1, P < 0.05). The dialysate lactate level was not affected in either tissue by large changes in the interstitial glucose concentration indicating that in neither tissue is blood glucose a significant source of lactate formation. 5. The blood flow effects on the dialysate glucose concentration are the likely consequence of probe glucose drainage artificially shifting the balance between the supply and consumption of interstitial glucose.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine↗
PubMed1993

Mechanism of enhanced insulin sensitivity in athletes. Increased blood flow, muscle glucose transport protein (GLUT-4) concentration, and glycogen synthase activity.

UNLABELLED: We examined the mechanisms of enhanced insulin sensitivity in 9 male healthy athletes (age, 25 +/- 1 yr; maximal aerobic power [VO2max], 57.6 +/- 1.0 ml/kg per min) as compared with 10 sedentary control subjects (age, 28 +/- 2 yr; VO2max, 44.1 +/- 2.3 ml/kg per min). In the athletes, whole body glucose disposal (240-min insulin clamp) was 32% (P < 0.01) and nonoxidative glucose disposal (indirect calorimetry) was 62% higher (P < 0.01) than in the controls. Muscle glycogen content increased by 39% in the athletes (P < 0.05) but did not change in the controls during insulin clamp. VO2max correlated with whole body (r = 0.60, P < 0.01) and nonoxidative glucose disposal (r = 0.64, P < 0.001). In the athletes forearm blood flow was 64% greater (P < 0.05) than in the controls, whereas their muscle capillary density was normal. Basal blood flow was related to VO2max (r = 0.63, P < 0.05) and glucose disposal during insulin infusion (r = 0.65, P < 0.05). The forearm glucose uptake in the athletes was increased by 3.3-fold (P < 0.01) in the basal state and by 73% (P < 0.05) during insulin infusion. Muscle glucose transport protein (GLUT-4) concentration was 93% greater in the athletes than controls (P < 0.01) and it was related to VO2max (r = 0.61, P < 0.01) and to whole body glucose disposal (r = 0.60, P < 0.01). Muscle glycogen synthase activity was 33% greater in the athletes than in the controls (P < 0.05), and the basal glycogen synthase fractional activity was closely related to blood flow (r = 0.88, P < 0.001). IN CONCLUSION: (a) athletes are characterized by enhanced muscle blood flow and glucose uptake. (b) The cellular mechanisms of glucose uptake are increased GLUT-4 protein content, glycogen synthase activity, and glucose storage as glycogen. (c) A close correlation between glycogen synthase fractional activity and blood flow suggests that they are causally related in promoting glucose disposal.

Adult↗
PubMed1993

[Evaluation of 4 immunobiochemical/molecular methods for the identification of Trypanosoma cruzi and Trypanosoma rangeli strains].

In American man can be infected with two trypanosomes: Trypanosoma cruzi, the etiological agent of Chagas' disease and Trypanosoma rangeli, a suspected nonpathogenic parasite. In this communication are presented 4 methods in order to improve the current knowledge about the specific identification of these parasites. Using the SDS-PAGE technique it was possible to differentiate between T. rangeli. and T. cruzi based in at less 4 protein bands with a relative molecular weights of 93, 77-73, 63 and 54-52 KDa. These polypeptides were found only in T. rangeli electrophoretic profiles. An ELISA test showed that the antigenic composition found in the enzyme cisteine proteinase (cruzipain) is specific for T. cruzi epimastigotes. Antigenic analysis by Western blot assay, proved that T. rangeli and not T. cruzi present antigenic bands with a Mr of 142, 63, 54, 51, 49, 43, 39 and 24 KDa. Finally, using the Southern blot procedure, it was confirmed that SAPA, a DNA sequence originally identified in the T. cruzi, genome, is absent in T. rangeli nuclear DNA. These initial observations revealed that it is possible to identify both parasites using the described methods, however further works are required to clarify the biochemical, immunological and molecular relationship between T. rangeli and T. cruzi.

Animals↗
PubMed1992

The major cysteine proteinase (cruzipain) from Trypanosoma cruzi is encoded by multiple polymorphic tandemly organized genes located on different chromosomes.

We demonstrate that cruzipain, the major cysteine proteinase of Trypanosoma cruzi epimastigotes, is encoded by a large number of tandemly arranged genes. Restriction enzyme analysis of 20 clones containing complete repeat units of the gene, as well as sequencing of 2 of these clones, and comparison with previously published partial sequences, indicated that the sequence is conserved among the repeat units, although polymorphisms clearly exist. The repeat units contain an intergenic region of 528 bp and coding regions for pre- and pro-enzyme, a central domain and a C-terminal extension. The predicted amino acid sequences of these regions indicated a sequence identity of 30, 60, 70 and 36%, respectively, when the T. cruzi sequence was compared with the sequence of a similar cysteine proteinase from Trypanosoma brucei. Studies by pulsed field gel electrophoresis, complemented with restriction analysis, indicated that the clusters are located on 2-4 different chromosomes in several parasite isolates.

Amino Acid Sequence↗